During oil well operation, a bottom-hole pump is typically actuated by a string of sucker rods; the uppermost rod is known as the polished rod or polish rod. To accomplish the pumping action from the well, reciprocating motion is provided to the sucker rod string by suspending the polish rod from a rocking beam by means of a suitable hanger.
The vast majority of oil wells have deviations from the vertical axis. Therefore, reciprocating motion of the sucker rod string in wells results in uneven wearing of both the sucker rods and well tubing. Intermittent rotating action (usually clockwise direction looking down the well) can be provided by a rod rotator to rotate the sucker rod string, resulting in a more even wearing of the sucker rods and well tubing. Further, this rotation can prevent unwanted unscrewing of rods and, when used in conjunction with rod scrapers, can reduce the build-up of wax and paraffin on the surfaces of tubing and sucker rods.
A polished rod is typically supported by a thrust bearing within the rotator by the means of a polished rod clamp. The clamp is used to create a friction connection with the polished rod and prevent it from moving downwards through the cylindrical opening in the rod rotator.
Vertical positioning adjustment between the string and the hanger is necessary from time to time. However, this is only possible by repositioning the polished rod clamp on the polished rod.
Unlike the reciprocating and rotary movements, which have been subject to numerous technological advancements over time, the vertical positioning adjustment has received little attention. The operation of a vertical positioning adjustment is a technically challenging operation requiring a high degree of skill. It also carries a significant amount of risk due to the possibility of failure of the friction connection between the polished rod clamp and polished rod, which can result in the polished rod, and the sucker rod string, falling downhole and leading to damage of the downhole equipment.
Accordingly, there is need to provide a method and apparatus that can overcome the short-comings of the prior art with respect to vertical height adjustment. More particularly, an apparatus is needed that can provide an improved method of vertically restraining the polished rod while offering convenient and safe vertical positioning adjustment of the sucker rod string.